[Variation in the Temperature Sensitivity of Surface Litter Respiration and Its Influencing Factors]

Surface litter respiration is a major component of soil respiration in the carbon cycle of terrestrial ecosystems, and studying the variation in the temperature sensitivity of surface litter respiration and its influencing factors is important for the accurate understanding of the regional soil carbon cycle. In a typical locust plantation (Robinia pseudoacacia L.) ecosystem in a small watershed in Wang Donggou of Loess Plateau, China, three surface litter control treatments were established: ① control treatment, ② litter removal treatment, and ③ doubled litter treatment, for studying the interannual variation (2009-2013) in the temperature sensitivity of surface litter respiration and its influencing factors. The interannual variability in the temperature sensitivity of surface litter respiration was statistically significant (P<0.05). It ranged from 4.15 in 2012 to 6.67 in 2010, with mean value of 5.10 and a coefficient of variation of 19% in the control treatment, and from 1.77 to 6.52, with mean value of 3.36 and a coefficient of variation of 56% in the doubled litter treatment. It was closely related with annual surface litter biomass, annual mean soil moisture content, and the interplay between annual surface litter biomass and annual mean soil moisture content (P<0.01). Moreover, the contribution to temperature sensitivity of surface litter respiration from soil moisture was greater than that from surface litter biomass (control treatment: 2.68 vs. 2.04, respectively; doubled litter treatment: 1.37 vs. 0.69, respectively). Additionally, under the doubled litter treatment, temperature sensitivity of surface litter respiration decreased by 34%. In the artificial locust plantation ecosystem, over 50% of surface litter carbon was kept under the control treatment [215 g·(m²·a)^-1 vs. 113 g·(m²·a)^-1], but only 24% of surface litter carbon was kept under the doubled litter treatment [430 g·(m²·a)^-1 vs. 326 g·(m²·a)^-1], which implied that the soil carbon reserves in the plantation ecosystem will not increase with an increase of surface litter biomass in the Loess Plateau, China. Therefore, investigating the relationships among soil moisture, surface litter biomass, and surface litter biomass control measures are useful for the accurate understanding of the regional soil carbon cycle.